Method for covering a printing roller

ABSTRACT

A printing roller having an extruded covering sleeve, in one form having electrical characteristics for optimum electrically assisted printing; and in another form having optimum solvent resistance. A method and apparatus for applying such sleeves including a belt wrapped at least 360 degrees about the sleeve and driven by rotation of the roller and moved progressively along the sleeve to apply the sleeve to the roller and to remove gaseous entrapment, and preferably also to disperse a reservoir of adhesive over the interface between the roller and sleeve.

July 18, 1972 MaccALLUM EI'AL 3,677,856

METHOD FOR COVERING A PRINTING ROLLER Filed Aug. 25, 1969 2 Sheets-Sheet 1 l,\ '5.\ was JAMES 4. MC (ALL 0M [/64 MA? 5 //a WARD D A65 4. COBERLEY m% M 742 A'IVURXEYS July 18, 1972 MaOcALLUM ETI'AL 3,677,856

METHOD FOR COVERING A PRINTING ROLLER Filed Aug. 25, 1969 2 Sheets-Sheet 2 5 Z INVENTORfi JAMES 4. Ma (44 u/v/ V54 MA? 5 /%WAEO D 4. (abs/Q57 BY I M I .-\TTOR.\'EYS United States Patent 3,677,856 METHOD FOR COVERING A PRINTING ROLLER James A. MacCallum, Danville, Ill., Velmar E. Howard, Veedersburg, Ind., and Daniel A. Coberley, Danville, lll., assignors to Hurletron Incorporated, Danville, 11].

Filed Aug. 25, 1969, Ser. No. 852,784 Int. Cl. B65h 81/00 U.S. Cl. 156-187 4 Claims ABSTRACT OF THE DISCLOSURE A printing roller having an extruded covering sleeve, in one form having electrical characteristics for optimum electrically assisted printing; and in another form having optimum solvent resistance. A method and apparatus for applying such sleeves including a belt wrapped at least 360 about the sleeve and driven by rotation of the roller and moved progressively along the sleeve to apply the sleeve to the roller and to remove gaseous entrapment, and preferably also to disperse a reservoir of adhesive over the interface between the roller and sleeve.

SUMMARY OF THE INVENTION The present invention relates to a method and apparatus for applying a sleeve to a printing roller.

An object of the invention is to provide an improved method and apparatus for covering a printing roller for electrically assisted printing systems.

A significant contribution of the present invention resides in the provision of a method and apparatus for applying a new covering to a printing roller at the users plant.

Still another object of the invention resides in the provision of a method and apparatus for applying a covering to a printing roller with greatly improved speed and efiiciency.

A feature of the invention resides in the provision of a method and apparatus for providing a protective covering for a conventional gravure impression roller.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat diagrammatic elevational view of the general arrangement of an apparatus in accordance with the present invention, with certain parts broken away and shown in section;

FIG. 2 is a somewhat diagrammatic horizontal sectional view taken generally along the plane represented by the line II-II of FIG. 1; and

FIG. 3 is an enlarged somewhat diagrammatic vertical sectional view showing certain preferred features of construction for an apparatus otherwise in accordance with FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrical printing roller, for example is an electrically assisted gravure printing system, is considered to be the most critical component because of the stringent and relatively narrow electrical requirements for such roller.

Conventional gravure impression rollers used in presses without the application of electric potential are limited in their advantageous characteristics because of the need for solvent resistance in the printing environment. Accordingly, optimum thermal conduction and resilience, for

example, have not been achieved in the conventional gravure impression roller. It is conceived that the provision of a sleeve cover, for example, formed of heat shrinkable material, will enable the use of a covering with excellent chemical and abrasion resistance, while the underlying substrate of the roller can have optimum thermal conduction and resilience. For example, the outer covering sleeve may be of neoprene, while the material of the substrate may be of natural rubber or other material with thermal conductivity and resilience substantially equivalent to that of natural rubber. This permits not only longer life, but higher press speeds. When excessive wear or catastrophic failure takes place, the covering sleeve is simply replaced. Such replacement can take place at the users plant, thus avoiding the delay due to shipping and the like which is generally the case at present.

In an electric printing roller, in addition to conventional parameters, one needs an electrical parameter critically related to the printing system. Such printing systems include those utilizing direct current potential and alternating current potential, for example.

By way of example, in an electrically assisted gravure printing system, printing conditions are encountered whereby portions of the impression roller contact the design cylinder to print a partial web. Using an applied direct current potential, for example, such contact interferes with the electrical function and the amount of assist becomes a compromise. With the use of the extruded sleeve configuration contemplated herein, it is entirely practical to use a partial covering of the impression roller, thus permittting an adjustment of the width of the conducting surface to correspond to that of the web without any change of the basic impression roller.

In the case of electrically assisted printing, when an electrical property is required of the sleeve, the present invention provides an optimized geometry enabling precise control of the parameter in manufacturing and in auditing. Conventional rollers must be refaced frequently to extend the life of the roller with a consequent progressive reduction in diameter. This change adversely aiTects the electrical properties. When the covering sleeve configuration of the present disclosure is replaced, satisfactory control for the electrical parameters is maintained simply by the proper selection of the thickness of the replacement covering sleeve. Although the sleeve cover may be refac'ed, one has a satisfactory control for the electrical parameters by maintaining a defined thickness.

Replacement of the sleeve for any roller may be done locally and in a few hours. Where rollers must be returned to the vendor and revulcanized as with prior art impression rollers, a time loss of several weeks commonly results. Rollers are heavy and consequently shipping costs are high.

With respect to the method and apparatus of the present invention, three particular objectives were found to be extremely important for a successful application of a sleeve on a roller or cylinder;

(a) A means to prevent gaseous entrapment.

(b) A means to increase circumferential tautness to the finished covering.

(c) A means to apply a uniform layer of adhesive between the sleeve and roller or cylinder.

To accomplish these objectives the present invention provides and apparatus for applying a heat-shrinkable sleeve to a printing roller, the apparatus comprising a roller support which is rotatable on a vertical axis and which is so shaped as to receive the lower journal of the printing roller and to support the roller during insertion into a sleeve. A means to rotate the roller at a variable speed is provided fixed to the rate of rise of a circumferential heater. The heater is so constructed as to permit convection to preheat the sleeve and to provide a maximum average radiant watt density of 80 watts per square inch (variable). As will hereinafter be described in detail, a belt is wrapped for at least 360 about the sleeve and is tensioned to exert uniform pressure on the sleeve. Energy is then applied, for example, heat energy by means of the heater, tending to cause the sleeve to constrict onto the roller. A driving force is applied to produce the rotation of the roller and to cause the belt to move progressively along the axis of the roller to smoothly apply the sleeve to the roller and to progressively remove entrapped gases. In one embodiment, a reservoir of adhesive is formed between the roller and sleeve at the lower portion thereof, the belt serving to progressively move the reservoir upwardly to distribute the adhesive over the interface between the roller and sleeve.

By way of preferred example, the sleeve indicated at in the drawings may be an extruded sleeve of continuous homogeneous annular cross-section and of a thickness of not greater than about A1". For a printing roller for a direct current assisted printing system, the sleeve may be of an elastomer material having a resistivity between about 10 to 10- ohm-centimeters. For an electrical printing roller for an alternating current electrically assisted printing system, the sleeve may be of a dielectric elastomer material having a dielectric constant between about 2 and 40. When the printing roller is to be used in a conventional gravure printing system, for example, without electrical potential applied, the sleeve may be formed of a solvent resistant elastomer material. In each instance, the sleeve may be of an irradiated heat-shrinkable neoprene material having a thickness of not greater than about A".

Referring to FIG. 1, a printing roller 11 is shown mounted for rotation on a vertical axis by mounting means 12 which in the detailed embodiment of FIG. 3 may comprise a conventional chuck. The mounting means 12 is so constructed as to be capable of stably supporting the roller with its upper end free to receive the sleeve 10 thereon. The details of the mounting means 12 will be described at a later point in reference to FIG. 3.

For applying a driving force to rotate the roller on its axis, a motor 14 is provided having reduction gearing at 15 and an output shaft at 16 with a sprocket 17 thereon. The sprocket 17 drives a sprocket 18 by means of a sprocket chain indicated at 19, and shaft 20 of sprocket 18 is connected with the mounting means 12 such as the chuck indicated in FIG. 3 so as to drive the chuck and the roller 11 which is fixedly secured therewith.

In surrounding relation to the roller and sleeve is a heater 22. The heater 22 is so constructed as to permit convection to pre-heat the sleeve 10 and to provide a maximum average radiant watt density of 80 watts per square inch. The wattage supplied by the heater 22 is adjustable so as to be coordinated with the rate of movement of the heater and other components as will hereinafter he described. The heater 22 is shown as being mounted by means of a bracket 23 on a backing plate or carriage 24 having rollers such as indicated at 25 which are vertically guided by means of guide rods 26. The backing plate 24 is shown as being coupled to a threaded shaft 27 on which at the lower end is a sprocket 28 driven by means of a sprocket chain 29 from a sprocket 30 on the motor output shaft 16. Thus the rate of upward movement of the heater 22 is coordinated with the rate of rotation of the roller 11.

Referring to the upper part of FIG. 1, a means is indicated at 34 for retaining the upper end of the roller 11 during a sleeve applying operation. The retaining means or yoke 34 includes a collar 35 which is slidably adjustable along a guide rod 36 so as to accommodate different length rollers 11. The yoke 34 is swingable in a horizontal plane about the guide rod 36 so as to accommodate the assembly of the sleeve 10 over the roller 11. The yoke 34 is then positioned and retained with centering screw 38 in alignment with the upper end shaft of the roller 11, the centering screw 38 being threadedly adjusted against the end of the shaft to retain the shaft while permitting rotation thereof.

For the purpose of uniformly and smoothly applying the sleeve 10 to the external peripheral surface of the roller 11, an endless belt 40 is provided which in operation is driven in the direction of its length and is progressively moved along the length of the sleeve from the lower end thereof to the upper end thereof at a rate coordinated with the rate of movement of the heater 22. As shown at the lower part of FIG. 1, the belt 40 is guided by means of guide pulleys 41 and 42 carried on the backing plate 24. The roller 11 is rotated in such a direction as to drive the belt in the direction of arrows 43 and 44. The guide pulleys 41 and 42 are arranged so that the belt tightly encircles the entire periphery of the sleeve.

FIG. 2 is a horizontal sectional view illustrating a preferred belt guide configuration for the apparatus otherwise as illustrated in FIG. 1. In this arrangement, backing plate 24 carries a belt 50 which is wrapped in excess of 1 turn about the sleeve 10 and is carried by means of guide pulleys 51 and 52 which are freely rotatable on brackets 53 and 54. The driving of the chuck 12, as illustrated in FIG. 1, results in the rotation of the sleeve 10 so as to drive the belt 50 as indicated by arrows S5 and 56, the direction of rotation of the roller 11 being indicated by arrow 57. In the preferred arrangement of FIG. 2, the belt 50 makes slightly more than 1 turn about the sleeve 10 so that there is a corresponding complete twist in the section of belt indicated at 50a. By way of example in one operating arrangement, the pulley 51 had an inclination of 67 /2" to the horizontal as projected onto a vertical plane such as represented at Al, the axis of rotation of a pulley 51 tilting from right to left moving upwardly along the axis as viewed from a point such as indicated at A1 in FIG. 2. Viewing pulley 51 in a vertical plane as represented at B1, the axis of rotation would be inclined at an angle of 87 to the horizontal. Viewing the pulley 51 from an observation point such as indicated at B1 in FIG. 2, the axis would extend from right to left with respect to the upward direction along the axis.

Referring to the pulley 52 as projected onto the vertical plane A2, the axis of rotation of the pulley would form an angle of 67 /2 to the horizontal. Viewing the pulley 52 from a point of observation A2, the axis of rotation would extend from left to right as viewed in the direction upwardly along the axis. With respect to the vertical plane B2, the axis of rotation of pulley 52 would form an angle of 87 to the horizontal. Viewing the pulley from a point of observation B2, the axis of rotation would progress from right to left with respect to the upward direction along the axis of rotation. For the purpose of tensioning the belt 50 to the desired degree, pulley support 53 may be slidable in the direction of arrow 60 by means of adjusting screw 61 having an operating knob 62.

Referring to FIG. 3, during the time that the sleeve 10 is being assembled on the roller 11, the belt 50 may be disposed on a lower clamping ring 64. Throughout the operation of the belt and its movement along the length of the sleeve, adjacent portions of the belt in the region such as indicated at '65 have their adjacent edges in contiguous adjoinrnent. The extent of this region of contiguous adjoinment is indicated by the doubled headed area 66 in FIG. 2. By this arrangement, a substantially continuous pressure encirclement of the sleeve is provided to prevent passage of gas downwardly past the belt.

FIG. 3 illustrates the manner in which the sleeve may be retained at its lower end during the applying operation. Specifically, lower clamping ring 64 is shown displaced downwardly so as to receive a lower annular edge 10a of the sleeve into a space between the ring 64 and a cup ring 70. The cup ring 70 has a diameter approximately corresponding to the diameter of the roller 11 and is bevelled as indicated at 70a. At its top edge 70b, the cup ring provides a seal against the bottom of the roller 11.

With respect to the particular examples of printing rollers given herein, the roller 11 would be comprised of a metal core 72 having an elastomer layer 73 bonded thereto. For this type of roller, as shown in FIG. 3, the upper edge 70b of cup plate 70 will butt against the elastomer substrate 73 in sealing relation thereto so as to prevent the passage of adhesive from the surface of the substrate 73 into the interior of the cup ring 70. The cup ring 70 is held up against the bottom of the roller 11 by means of springs such as that indicated at 75 in FIG. 3. The sleeve is placed between the bevel 70a and a cooperating bevel 64a of clamping ring 64, sometimes with the aid of a small hand-held forced air heater. The clamping ring 64 is constructed to adjust along the roller axis to provide for variations in rollers and to press the bevel '64a toward the bevel 70a to form the clamp for the lower edge 10a of sleeve 10.

A similar clamping means is indicated at 78 at the top in FIG. 1 for securing the top edge 10b of the sleeve 10. The clamping device 78 may utilize similar cooperating bevel faces and seals off the top of the sleeve. A relief valve 79 is designed into the top clamping device 78 to provide a controlled release of gases from between the sleeve 10 and roller 11 during application.

By way of example, the relief valve 79 may provide an interior pressure limit of .6 inch of mercury. The restriction provided by the presence of valve 79 results in the inflation of the sleeve 10 during application of the sleeve to the roller and aids in a concentric assembly as well as preventing wrinkles from forming above the belt 50 (referring to FIGS. 2 and 3) which would adversely affect the uniform distribution of the adhesive over the interface between the sleeve and roller. In some cases, air may be pumped into the sleeve to inflate the same initially.

For the purpose of distributing adhesive to the interface between the sleeve and roller, an annular cup is provided as indicated at 80 in FIG. 3 defining a reservoir 81 for an adhesive. Cup 80 is designed to hold a desired amount of adhesive and is of a flexible material so as to progressively collapse as the belt 50 moves upwardly thereacross. In operation the belt 50 spirals up the revolving roller 11 and sleeve 10 immediately below the heater 22, the belt 50 and heater 22 moving progressively from the position shown in FIG. 3 in the upward direction so as to progressively collapse the cup 81 and move the body of adhesive upwardly with the belt 50. As the belt 50 progresses upwardly along the sleeve 10 it pushes the excess adhesive and the undesirable gas bubbles upwardly and eventually off the upper end of the roller substrate 73. The upper clamp 78 is designed to accept the overflow of adhesive. Together, the belt compression and the reservoir formed by the adhesive prevent detrimental air entrapment. The belt tension is designed to control the thickness of the adhesive layer as well as to control the degree of tightness of the sleeve 10 over the roller substrate.

As an example, the adhesive which is indicated at 84 in FIG. 3 may comprise a two-part epoxy having a viscosity of about Saybolt-seconds at the operating temperature at which the adhesive is being distributed over the interface between the sleeve and roller.

As an alternative means of applying adhesive to the interface between the roller and sleeve, the adhesive may be injected into an annular region at the lower end of the sleeve by means of a syringe type pump. The pump may be provided with a needle-like nozzle which pierces the sleeve from the outside. After the adhesive is injected, the nozzle is removed and the opening is sealed. This alternative is particularly useful, for example, where the sleeve is to have a lesser length than the roller and is to be applied to a central portion of the roller for example. The belt would then apply the adhesive over the area of the interface by its progressive movement over the sleeve.

Injection of adhesive is also successful by the use of interconnecting flexible tubes extending through the lower clamping ring 64 and into communication with the reservoir 81. The adhesive may be applied over the surface of the roll substrate prior to the application of the sleeve to the roller, as another alternative.

The annular cup may be of paper and the like, so that it will collapse as the belt 50 moves therealong.

SUMMARY OF OPERATION In operation, the lower end of the roller 11 is secured in the mounting means 12, after which the sleeve 10 is inserted thereover. The lower end of the sleeve 10 fits into a clamping mechanism such as indicated at 64 and 70 which then closes to retain the sleeve end 10a.

Motor 14 is then started to rotate the roller and sleeve assembly on the vertical axis and to progressively move the carriage 24 vertically. The rotation of the sleeve 10 drives the belt 40, FIG. 1, or 50, FIGS. 2 and 3, and the belt 40 or 50 moves upwardly from an initial position such as indicated in FIG. 3 together with the heater 22. The belt 50 moves progressively off of the lower clamping ring '64 and progressively collapses the cup 80 to move the annular body of adhesive 84 upwardly along with the belt so that the adhesive is uniformly distributed over the interface between the roller and sleeve. The belt compression together with the annular body of adhesive prevent detrimental air entrapment and forces the excess adhesive and undesirable gas bubbles upward and eventually oif the top end of the roller substrate 73, gases being discharged by means of the relief valve 79 at the top of the assembly, FIG. 1.

We claim as our invention:

1. The method of covering a printing roller which comprises placing a sleeve on the printing roller with the sleeve surrounding the roller, the sleeve being disposed in overlying relation to the external peripheral surface of the roller with an interface therebetween, supplying a reservoir of adhesive between the roller and the sleeve, wrapping a belt for at least 360 about the sleeve and tensioning the belt to exert uniform pressure on the sleeve, and driving the belt while so wrapped in the direction of its length and also progressively upwardly along the axis of the roller to distribute the adhesive over the interface between the roller and the sleeve and to smoothly apply the sleeve to the roller.

2. A method in accordance with claim 1 with the further step of applying heat energy to the sleeve material and progressively along the length thereof, in advance of the belt.

3. The method of covering a printing roller which c0m prises placing a heat shrinkable sleeve of homogeneous continuous annular cross section over the roller with the sleeve surrounding the roller, wrapping a belt about this sleeve and tensioning the belt to exert uniform pressure on the sleeve, heating the sleeve to constrict the sleeve onto the roller, applying an adhesive to the region between the roller and the sleeve, and applying a driving force to rotate the roller and to drive the belt in the direction of its length and also progressively along the axis of the roller to uniformly distribute the adhesive between the roller and the sleeve and to smoothly apply the sleeve to the roller.

4. A method according to claim 3 further comprising applying the adhesive to a reservoir in advance of the 7 8 belt, heating the sleeve initially at a region thereof over- 2,960,753 11/ 1960 Robertson 156187 lying the reservoir, and heating the sleeve at successive 3,453,163 1/1969 Mills et a1. 156 195 regions thereof progressively along the length of the 3,126,306 3/1964 Sherman 156-187 sleeve in advance of the belt.

5 CARL D. QUARFORTH, Primary Examiner Refereuces Cited G. G. SOLYST, Assistant Examiner UNITED STATES PATENTS 3,533,883 10/1970 Gartaganis et al. 156-195 3,366,719 1/1968 Lueders 156-487 321 

